Last week I encouraged you to collect general knowledge. Viking trade routes, anime, Rothko paintings, architecture, typography, bluegrass standards -- where ever your interests lead you.

For these kinds of things, it may be hard to write a note though. You could certainly write down something, but it's unlikely that you'll develop a few paragraphs of a coherent thought about lots of random things.

James Webb Young said to use index cards for that. That would certainly work, but I recommend using spaced-repetition card software instead.